一种应用于MCU的低温漂RC振荡器设计

针对高稳定性MCU的应用需求,设计了一种低温度灵敏度的RC振荡器.采用平均电压反馈电路降低比较器延迟对振荡器输出频率的影响,采用温度补偿技术补偿温度对振荡器输出频率的影响,实现RC振荡器高稳定性输出.设计了一种选频网络,实现宽频率范围内高精度输出,满足MCU对多种时钟频率的需求.RC振荡器基于SMIC 110 nm C...     

Modulating the Verwey Transition of Epitaxial Magnetite Thin Films by Ionic Gating

Understanding the Verwey transition in magnetite (Fe₃O₄), a strongly correlated magnetic oxide, is a one-century-old topic that recaptures great attention because of the recent spectroscopy studies revealing its orbital details. Here, the modulation of the Verwey transition by tuning the orbital configurations with ionic gating is reported. In epitaxial magnetite thin films, the insulating Verwey state can be tuned continuously to be metallic showing that the low-temperature trimeron states can be controllably metalized by both the gate-induced oxygen vacancies and proton doping. The ionic gating can also reverse the sign of the anomalous Hall coefficient, indicating that the metallization is associated with the presence of a new type of carrier with competing spin. The variable spin orientation associated with the sign reversal is originated from the structural distortions driven by the gate-induced oxygen vacancies.     

Dry inoculation methods for nonfat milk powder

Carriers with inoculated microorganisms are often used to validate low-moisture food safety interventions. In this study, we evaluated dry inoculation methods using silicon dioxide (SiO₂) and a small portion of nonfat milk powder (NFMP) as dry carriers for NFMP. Silicon dioxide was characterized by vapor sorption analysis. One milliliter of inoculum of a 5-strain Salmonella cocktail (serovars Agona, Reading, Tennessee, Montevideo, and Mbandaka) or Enterococcus faecium NRRL B-2354 was inoculated onto 1 g of SiO₂ or 10 g of NFMP as carriers. Both inoculated carriers were air-dried for 72 h [22°C, relative humidity (RH) ～30%], equilibrated to water activity (a_w) 0.25 ± 0.02 (24 h at 22°C, RH 25%), and mixed with preconditioned NFMP (a_w = 0.25 ± 0.02) to reach an inoculation level of 8.2 ± 0.2 log cfu/g. Inoculated NFMP was stored at 22°C, RH 25%, and its bacterial populations were monitored for 30 d. Both sets in equilibrated NFMP were subjected to isothermal treatments in closed aluminum cells at 85, 90, and 95°C. Silicon dioxide maintained moisture content (0.29 ± 0.03%, dry basis) at different water activities. The NFMP inoculated with both carriers exhibited stable bacterial populations over 30 d at 22°C. Strains in NFMP inoculated with SiO₂ showed equal or higher D-values but equal z-values compared with those inoculated with a small portion of NFMP. Enterococcus faecium exhibited comparable thermal resistance to Salmonella under all tested conditions. This study supports E. faecium as a Salmonella surrogate in thermal processing of NFMP and the use of SiO₂ to inoculate NFMP.     

Structural Optimization Design of a Typical Adhesive Bonded Honeycomb-Core Sandwich T-joint in Side Bending Using Multi-Island Genetic Algorithm

Applied Composite Materials - Sandwich structure T-joints are increasingly broadly applied in aviation and aerospace industries due to the need for lightweight design. This paper deals with the...     

城市轨道交通站点影响域界定的若干关键问题

轨道交通作为以轨道运输为主要 技术特征的城市公共交通客运立体系统,成 为近年来城市公共交通发展的典型代表和 重大变化。随着轨道交通线路及站点快速地 植入城市空间,会产生一系列的新空间、新现 象、新规律。站点影响域作为轨道交通植入 城市空间后产生的重要节点区域,对其加以界 定并进行深入专项研究有重要的实践意义。 通过对城市轨道交通与城市空间相关研究成 果的梳理,总结出交通导向、环境导向、空间 导向等三种概念类型;进而,在分析轨道交 通站点、行人、城市空间等关键要素相互影 响的基础上,站点影响域的概念自然生成; 提出了多学科融合、城市设计精细化、大数 据探索等时代趋势下站点影响域界定的创新 机制——以“行为规律”为纽带,建立“交通 方式—行为规律—城市空间”这一组科学联 系,基于此提出未来精确划定站点影响域的 “边界”这一重要课题的关键问题。     

高密度电法在滑坡地质灾害勘查中的应用

受核工业天水工程勘察院委托,勘查单位在甘肃省天水市北山中梁地质灾害调查区开展高密度电法探测工作,在收集整理有关甘肃省天水市北山中梁地质灾害调查资料基础上,通过高密度电法探测工作,初步查明调查区滑坡体滑动面位置及埋深等情况,为科学治理滑坡体提供科学依据.     

利用天然粉石英制备中空硬硅钙石二次粒子研究

采用动态水热法 ,以江西产天然粉石英、河北井陉产石灰为原料 ,加入少量的氧氯化锆为添加剂合成硬硅钙石晶体。结果表明 ,单纯使用粉石英与石灰为原料无法制备出具有中空结构的硬硅钙石二次粒子 ,硬硅钙石体积密度较大 ,所制备的硬硅钙石纤维发育不好 ;适量加入氧氯化锆添加剂可生成具有低密度、中空结构的硬硅钙石二次粒子 ,同时可生成结晶良好 ,直径 10 0nm左右的硬硅钙石纤维。此工艺提供了廉价制备超轻硬硅钙石制品的可能。     

杨浦大桥箱形钢主梁焊接工艺研究

本文详细论述了杨浦大桥主桥钢结构箱形主梁的焊接工艺和技术措施;着重分析了控制箱形梁变形,防止层状撕裂的焊接工艺程序;探讨了适合于箱形梁焊接的坡口形式;提出了箱形梁单面坡口自动角焊的焊接新工艺。     

砂卵石地层盾构带压开舱泥膜闭气能力研究

本研究在考虑非饱和土内的水、气渗透系数随饱和度变化的基础上通过Geostudio Air/w数值模拟,分析了开舱气压、泥膜厚度和泥膜干裂等因素对泥膜的闭气能力的影响。结果表明:1)当开舱气压小于泥膜进气值与地下水压之和时,泥膜具有良好的闭气能力;当开舱气压大于泥膜进气值与地下水压之和时,压缩空气将进入泥膜,排出孔隙内水分,泥膜内部逐步形成贯穿孔隙,闭气能力下降,开始漏气。2)增加泥膜厚度能大幅度降低开挖面空气逃逸流量,显著提高泥膜的闭气能力。3)泥膜干裂后,开舱气压产生小波动时(小于5 kPa),空气逃逸量可能突增几个数量级,泥膜丧失闭气能力。基于以上认识,成都轨道交通17号线一期TJ07标的带压开舱工程中设置的开舱压力为300 kPa,成功地在砂卵石地层完成了带压换刀作业。